U.S. patent application number 12/357987 was filed with the patent office on 2010-07-22 for regulated power supply.
This patent application is currently assigned to Phihong USA Corp. Invention is credited to Richard Frosch, Predrag Hadzibabic, Keith Hopwood, Glen Marchiony.
Application Number | 20100181930 12/357987 |
Document ID | / |
Family ID | 42336395 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100181930 |
Kind Code |
A1 |
Hopwood; Keith ; et
al. |
July 22, 2010 |
REGULATED POWER SUPPLY
Abstract
A circuit for producing a regulated output voltage and/or
current includes a rectifier to rectify an alternating current (AC)
input voltage and current to produce a rectified voltage and
current having a frequency. A regulator is coupled to the rectifier
to produce a regulated output based on the rectified voltage and/or
current. A pair of output terminals supply the regulated output to
a load The circuit does not include any capacitors that
substantially filter the frequency of the rectified voltage and
current.
Inventors: |
Hopwood; Keith; (Fremont,
CA) ; Frosch; Richard; (Bohemia, NY) ;
Hadzibabic; Predrag; (Bohemia, NY) ; Marchiony;
Glen; (Bohemia, NY) |
Correspondence
Address: |
FISH & RICHARDSON P.C.
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
Phihong USA Corp
Fremont
CA
|
Family ID: |
42336395 |
Appl. No.: |
12/357987 |
Filed: |
January 22, 2009 |
Current U.S.
Class: |
315/297 |
Current CPC
Class: |
H05B 45/385 20200101;
H05B 45/3725 20200101; H05B 45/37 20200101 |
Class at
Publication: |
315/297 |
International
Class: |
H05B 41/36 20060101
H05B041/36 |
Claims
1. A method of producing a regulated output, the method comprising:
receiving an alternating current (AC) voltage and current;
rectifying the AC voltage and current to produce a rectified
voltage and current having a frequency; regulating at least one of
the rectified voltage and rectified current to create a regulated
output, wherein the regulated output is produced without
substantially filtering the frequency of the rectified voltage and
current.
2. The method of claim 1 further comprising enabling the frequency
of the rectified voltage and current to pass to the regulated
output.
3. The method of claim 1 wherein the regulating produces a
regulated voltage.
4. The method of claim 1 wherein the regulating produces a
regulated current.
5. The method of claim 1 implemented with a circuit that does not
include capacitors that filter the frequency of the rectified
voltage and current.
6. The method of claim 1 implemented with a circuit that does not
include electrolytic capacitors.
7. The method of claim 1 further comprising: filtering high
frequencies from the regulated, rectified voltage and current to
reduce electromagnetic emissions.
8. The method of claim 1 wherein the frequency of the rectified
voltage and current is twice the frequency of the AC voltage and
current.
9. The method of claim 4 wherein rectifying the AC voltage
comprises full wave rectification to produce a constant polarity
waveform having a magnitude that varies over time in a
substantially similar manner as an absolute value of the AC
voltage's magnitude.
10. The method of claim 1 further comprising controlling the
regulation with a power factor controller that is operable to
control the amount of reactive power generated in producing the
regulated output.
11. The method of claim 1 wherein the load is a lighting device
comprising one or more light emitting diodes.
12. A circuit for producing a regulated output, the circuit
comprising: a pair of input terminals to receive an alternating
current (AC) voltage and current; a rectifier coupled to the input
terminals to rectify the AC voltage and current and to produce a
rectified voltage and current having a frequency; a regulator
coupled to the rectifier to produce a regulated output; and a pair
of output terminals to supply the regulated output to a load;
wherein the circuit does not include any capacitors to
substantially filter the frequency of the rectified voltage and
current.
13. The circuit of claim 12 wherein the frequency of the rectified
voltage and current is allowed to pass to the regulated output.
14. The circuit of claim 12 wherein the regulated output is
produced without substantially filtering the frequency of the
rectified voltage and current.
15. The circuit of claim 12 wherein the regulated output comprises
a regulated voltage.
16. The circuit of claim 12 wherein the regulated output comprises
a regulated current.
17. The circuit of claim 12 wherein the circuit is arranged so
that, during operation, current is drawn from at the input
terminals substantially in phase with the rectified voltage.
18. The circuit of claim 12 further comprising: one or more
capacitors to filter high frequencies for controlling
electromagnetic emissions.
19. The circuit of claim 12 wherein the rectifier is a full-wave
rectifier that produces a constant polarity waveform having a
frequency twice the frequency of the AC voltage and a magnitude
that varies over time in a substantially similar manner as an
absolute value of the magnitude of the AC voltage.
20. The circuit of claim 12 further comprising: a feedback loop
with a power factor controller for controlling the regulator,
wherein the power factor controller is operable to control an
amount of reactive power created by producing the regulated
output.
21. A system comprising: an alternating current (AC) power source;
a circuit coupled to the AC power source for producing a regulated
output from the AC power source voltage; and a light fixture
coupled to the circuit to receive the regulated voltage, wherein
the light fixture comprises one or more light emitting diodes, and
wherein the circuit comprises: a pair of input terminals to receive
an alternating current (AC) voltage and current; a rectifier
coupled to the input terminals to rectify the AC voltage and
current and to produce a rectified voltage and current having a
frequency; a regulator coupled to the rectifier to produce a
regulated output based on the rectified voltage or current; and a
pair of output terminals to supply the regulated, rectified voltage
to a load; wherein the circuit does not include any capacitors to
substantially filter the frequency of the rectified voltage and
current.
22. The system of claim 21 wherein the circuit is operable to pass
the frequency of the rectified voltage and current to the regulated
output.
23. The system of claim 21 wherein the regulated output comprises a
regulated voltage.
24. The system of claim 21 wherein the regulated output comprises a
regulated current.
25. The system of claim 21 wherein the circuit comprises: one or
more capacitors to filter high frequencies for control of
electromagnetic emissions.
26. The system of claim 21 wherein the rectifier is a full-wave
rectifier that produces a constant polarity waveform having a
frequency of twice the frequency of the AC voltage and a magnitude
that varies over time in a substantially similar manner as an
absolute value of the magnitude of the AC voltage.
27. The system of claim 21 wherein the circuit further comprises a
feedback loop with a power factor controller for controlling the
regulator, wherein the power factor controller comprising circuitry
operable to control an amount of reactive power created by
producing the regulated output.
28. The system of claim 21 wherein the circuit does not include any
capacitors that filter the frequency of the rectified voltage and
current.
29. The method of claim 21 wherein the circuit does not include any
electrolytic capacitors.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a regulated power supply and, more
particularly, relates to a regulated power supply having a simple
design and a long life expectancy.
BACKGROUND
[0002] Regulated power supplies generally operate to provide a
relatively controlled output voltage or output current regardless
of input variations. They have a variety of applications, including
as power supplies for light emitting diode based light fixtures.
They have finite operating lives and their maintenance and/or
replacement can be costly and difficult.
[0003] Regulated power supplies include large capacitors, such as
electrolytic capacitors, to facilitate smoothing of its output
voltage.
SUMMARY OF THE INVENTION
[0004] In one aspect, a circuit for producing a regulated output
voltage and/or current includes a pair of input terminals to
receive an alternating current (AC) voltage and current, a
rectifier coupled to the input terminals to rectify the AC voltage
and current thereby producing a rectified voltage and/or current
having a frequency, a regulator coupled to the rectifier to produce
a regulated output and a pair of output terminals to supply the
regulated output to a load.
[0005] In a typical implementation, the circuit does not include
any capacitors (e.g., large electrolytic capacitors) that would
substantially filter the frequency of the rectified voltage and
current. Typically, therefore, the frequency of the rectified
voltage and current is allowed to pass through to the regulated
output. In some implementations, the circuit is arranged so that,
during operation, the supplied voltage substantially includes the
frequency of the rectified voltage.
[0006] In another aspect, a method of producing a regulated output
includes receiving an alternating current (AC) voltage and current,
rectifying the AC voltage and current to produce a rectified
voltage and current having a frequency, regulating at least one of
the rectified voltage and rectified current to create a regulated
output. The regulated output is produced without substantially
filtering the frequency of the rectified voltage and current. In a
typical implementation, therefore, the frequency of the rectified
voltage and current is allowed to pass to the regulated output. In
some implementations, regulating produces a regulated voltage,
current, or voltage and current.
[0007] The method is sometimes implemented with a circuit that does
not include capacitors that filter the frequency of the rectified
voltage and current. Moreover, such a circuit does not include
electrolytic capacitors.
[0008] According to some implementations, the method includes
filtering only high frequencies from the regulated, rectified
voltage and current (e.g., those specified to be filtered to reduce
electromagnetic emissions).
[0009] The frequency of the rectified voltage and current typically
is twice the frequency of the AC voltage and current. Rectifying
the AC voltage typically includes full wave rectifying, which
produces a constant polarity waveform having a magnitude that
varies over time in a substantially similar manner as an absolute
value of the AC voltage's magnitude.
[0010] In a typical embodiment, the method also includes
controlling the regulation with a power factor controller that is
operable to control the amount of reactive power generated in
producing the regulated output. In certain embodiments, regulating
the rectified voltage includes switching one or more transistors,
and the power factor controller controls a duty cycle associated
with the switching to maintain a substantially constant phase
relationship between voltage and current being delivered to the
load.
[0011] In some implementations, the method includes sensing voltage
and current being delivered to the load, determining average values
of the sensed voltage and sensed current and controlling the
regulation based on the average values of sensed voltage and sensed
current. Sensing the voltage and current being delivered to the
load can include isolating the signals representing the sensed
voltage and current from the voltage and current being delivered to
the load with one or more optical isolators.
[0012] In some embodiments, the load is a lighting device that has
one or more light emitting diodes. Other loads and applications
(e.g., motor controller applications) are possible as well.
[0013] In yet another aspect, a circuit for producing a regulated
output includes a pair of input terminals to receive an alternating
current (AC) voltage and current, a rectifier coupled to the input
terminals to rectify the AC voltage and current and to produce a
rectified voltage and current having a frequency, a regulator
coupled to the rectifier to produce a regulated output and a pair
of output terminals to supply the regulated output to a load. In
some implementations, the circuit does not include any capacitors
to substantially filter the frequency of the rectified voltage and
current. In some implementations, the circuit is arranged so that,
during operation, the supplied voltage and/or current substantially
includes the frequency of the rectified voltage. The frequency of
the rectified voltage and current is, in some instances, allowed to
pass to the regulated output.
[0014] In various implementations, the regulated output includes a
regulated voltage, a regulated current or a regulated voltage and
current.
[0015] In some embodiments, the circuit is arranged and operational
so that, during operation, current is drawn from at the input
terminals substantially in phase with the rectified voltage.
Certain implementations include one or more capacitors to filter
only high frequencies for controlling electromagnetic
emissions.
[0016] The rectifier may be a full-wave rectifier that produces a
constant polarity waveform having a frequency twice the frequency
of the AC voltage and a magnitude that varies over time in a
substantially similar manner as an absolute value of the magnitude
of the AC voltage.
[0017] The circuit, in some instances, includes a feedback loop
with a power factor controller for controlling the regulator. The
power factor controller is operable to control an amount of
reactive power created in producing the regulated output. The
feedback loop also can include a sensor to sense the voltage being
delivered to the load, a sensor to sense the current being
delivered to the load and one or more integrator circuits to
determine, based on the sensed voltage and sensed current,
respective average values for the sensed voltage and sensed
current. The power factor controller can be arranged to control the
regulator based on the average values of sensed voltage and sensed
current.
[0018] In some implementations, one or more optical isolators are
provided to isolate the respective voltage and current sensors from
the one or more integrator circuits.
[0019] In yet another aspect, a system includes an alternating
current (AC) power source, a circuit coupled to the AC power source
for producing a regulated output from the AC power source voltage
and a light fixture coupled to the circuit to receive the regulated
voltage. The light fixture can include one or more light emitting
diodes. The circuit includes a pair of input terminals to receive
an alternating current (AC) voltage and current, a rectifier
coupled to the input terminals to rectify the AC voltage and
current and to produce a rectified voltage and current having a
frequency, a regulator coupled to the rectifier to produce a
regulated output based on the rectified voltage or current and a
pair of output terminals to supply the regulated, rectified voltage
to a load. The circuit does not include any capacitors to
substantially filter the frequency of the rectified voltage and
current.
[0020] In a typical implementation, the circuit is operable to pass
the frequency of the rectified voltage and current to the regulated
output. The regulated output can include a regulated voltage,
current or voltage and current.
[0021] In some embodiments, the circuit includes one or more
capacitors to filter high frequencies for control of
electromagnetic emissions.
[0022] The rectifier, in some instances, is a full-wave rectifier
that produces a constant polarity waveform having a frequency of
twice the frequency of the AC voltage and a magnitude that varies
over time in a substantially similar manner as an absolute value of
the magnitude of the AC voltage.
[0023] Certain implementations of the circuit include a feedback
loop with a power factor controller for controlling the regulator.
The power factor controller has circuitry operable to control an
amount of reactive power created by producing the regulated output.
The feedback loop also can include a sensor to sense the voltage
being delivered to the load, a sensor to sense the current being
delivered to the load and one or more integrator circuits to
determine, based on the sensed voltage and sensed current,
respective average values for the sensed voltage and sensed
current. The power factor controller is arranged to control the
regulator, based on the average values of sensed voltage and sensed
current.
[0024] In a typical embodiment, the AC power source is
substantially unregulated. The system, in some implementations,
includes means for protecting the load from exposure to potentially
damaging current flow.
[0025] The system, including the circuit, typically does not
include any capacitors that filter the frequency of the rectified
voltage and current. The circuit does not include any electrolytic
capacitors.
[0026] In some implementations, one or more of the following
advantages are present.
[0027] For example, regulated output voltage and/or current can be
supplied to a load (e.g., a light fixture having one or more light
emitting diodes) substantially in phase with the absolute value of
the regulator circuit's AC input voltage. The circuit operates with
a high power factor and with low harmonic distortion. It is typical
that the power factor is about 0.9 or higher (e.g., 0.91, 0.92,
0.93, 0.94, 0.95, 0.96, 0.97 or higher). Also, it is typical that
the total harmonic distortion is below about 3% (e.g., below 2.5%,
2.0%, 1.5% or lower).
[0028] The regulator circuit does not require large capacitors such
as electrolytic capacitors (including, for example, aluminum,
tantalum capacitors), that tend to fail relatively quickly in
service, particularly as compared to other circuit elements in a
regulator circuit. Since such large capacitors are not required,
the regulator circuit's size and component count can be relatively
small.
[0029] In general, high efficiency can be realized over a wide
range of input voltage waveforms (e.g., sine waves, square waves,
etc.) while providing effectively regulated voltage and/or current
at its output. The regulator circuit generally produces a small
amount of heat during operation.
[0030] In general, an extended operating life can be expected.
Thus, the burden associated with maintaining, repairing or
replacing such regulator circuits can be reduced. This may be
particularly beneficial in applications, such as street lights that
use light emitting diodes, where the power supply may be in service
at a location that is difficult to access.
[0031] Moreover, since the circuit itself is relatively simple, so
too is the design, manufacturing and troubleshooting of the circuit
as well.
[0032] The circuit typically requires very little space, since it
does not require large capacitors and is generally implemented as a
single stage regulator.
[0033] The regulator circuit is highly effective as a regulated
power supply for applications that include light emitting diodes.
Indeed, it has been found that light emitting diodes operate
effectively when operated with the regulator circuit disclosed
herein without any noticeable flicker. Moreover, it has been found
that the regulator circuit does not harm the light emitting diodes
during operation.
[0034] The regulated power supply can be operable to protect itself
and its downstream circuit from damage due to exposure to unduly
high stress from such natural phenomenon as lightening strikes and
temperature and power fluctuations.
[0035] Typically, the regulator circuit eliminates the need for
separate power factor control and DC-to-DC conversion thus
significantly reducing the number of components required to produce
a regulated output.
[0036] Other features and advantages will be apparent from the
description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a schematic diagram showing an exemplary regulated
power supply circuit.
[0038] FIGS. 2A-2C show exemplary voltage waveforms that appear at
various points in the circuit of FIG. 1 during circuit
operation.
[0039] FIG. 3A-3C show measured operating parameters for a circuit
similar to circuit of FIG. 1 connected to a resistive load.
[0040] FIG. 4A-4D show measured operating parameters for a circuit
similar to circuit of FIG. 1 connected to a light emitting diodes
fixture.
DETAILED DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a schematic diagram showing an exemplary
implementation of a regulated power supply circuit 100 connected to
an unregulated alternating current (AC) power source 102 and to a
load 104. In a typical implementation, the load 104 includes one or
more light-emitting diodes. However, the load 104 can include any
type of electrical component or combination of electrical
components, whose operation might benefit from receiving regulated
power.
[0042] The illustrated circuit 100 includes a rectifier 106, a
regulator 108, a feedback loop with a power factor controller 110,
a pair of diodes 112a, 112b (which is optional) and a high
frequency output capacitor 114. The circuit 100 is generally
operable to supply regulated, rectified voltage to the load 104.
The voltage supplied to the load includes a low frequency
component, that typically is twice the frequency of the AC power
source 102 frequency. The magnitude of the voltage supplied to the
load 104 varies over time in a similar manner as the absolute value
of the magnitude of the AC power supply 102 voltage.
[0043] It is generally desirable that the circuit 100 be arranged
and operated in such a manner that the regulated, rectified AC
voltage supplied to the load 104 approximates the contours of an
ideal rectified (but not filtered) AC waveform as closely as
possible without too much distortion. A high level of distortion in
the regulated, rectified AC voltage could result in an excessively
high level of harmonic distortion associated with the circuit's 100
operation. It is generally desirable that percent total harmonic
distortion (thd) be maintained below about 3% (e.g., 2.5%, 2.0%,
1.5%, etc.).
[0044] The range of low frequencies that are allowed to pass to the
load 104 can vary from circuit to circuit depending on a wide range
of design considerations. Typically, however, the range includes at
least the frequency of the rectified voltage, which--for a full
wave rectifier--is twice the frequency of the AC power source 102
frequency. In some implementations, the range of frequencies
allowed to pass to the load 104 may be quite broader, including,
for example, substantially all frequencies up to about ten times
the line frequency, or substantially all frequencies up to about
one hundred times the line frequency.
[0045] Since the frequencies about twice the AC line frequency are
substantially allowed to pass to the load 104, the voltage and
current delivered to the load 104 are substantially in phase with
the absolute value of the circuit's 100 AC input voltage. This
facilitates achieving a high power factor and low total harmonic
distortion (THD).
[0046] In some implementations, the circuit 100 also is operable to
limit its peak input and/or output current to help protect the
circuit from becoming overloaded and destroyed or harmed by
exposure to unduly high currents.
[0047] The exemplary circuit 100 of FIG. 1 is a fairly simple,
single-stage regulator. It is simple to manufacture, has very few
components and, therefore, is fairly compact, easy to troubleshoot,
repair and maintain. The illustrated circuit 100 also has a
relatively high life expectancy, at least because it does not
include large capacitors, such as electrolytic capacitors, which
are found in some regulators and which tend to fail relatively
quickly in service, particularly as compared to the other circuit
elements in regulator circuits. Also, the circuit 100 is highly
efficient and tends to produce very little heat when operating.
This too tends to increase the circuit's life expectancy.
[0048] The illustrated circuit 100 includes a pair of input
terminals 116a, 116b that receive voltage (V.sub.IN) and current
from the AC power source 102. The rectifier 106 is connected to the
input terminals 116a, 116b and is generally operable to convert the
input AC voltage from the AC power source 102 to a rectified
voltage (V.sub.R) having a constant polarity at its output. The
rectified voltage (V.sub.R) has a magnitude that varies over time
in the same way as an absolute value of the AC input voltage
(V.sub.IN).
[0049] In a typical implementation, the rectifier 106 is a full
wave rectifier, which can include, for example, four diodes (not
shown) arranged in a bridge configuration. However, other rectifier
configurations, such as ones utilizing a pair of diodes and a
center tapped transformer, are possible as well.
[0050] The regulator 108 is connected to the rectifier's 106 output
and is generally operable to produce a regulated voltage and/or
current based on the rectified voltage and/or current.
[0051] In a typical implementation, the regulator 108 is a
switching regulator and includes one or more high frequency
switches that switch on and off. By adjusting the duty cycle of
these switches, that is the ratio of on time versus off time, the
voltage, current and/or power being delivered to the load 104 can
be controlled. Additionally, these switches can be operated to
limit the maximum current flowing through the circuit 100.
[0052] In some embodiments, the regulator 108 is a flyback
converter that includes one or more switches (e.g., transistors)
and one or more inductive elements (e.g., a transformer). In such
embodiments, the one or more switches operate to sequentially store
and release energy from the one or more inductive elements. The
switches typically have very high switching speeds ranging, for
example, from about 50 kHz to about 1 MHz.
[0053] The power factor controller 110 is generally operable to
control the duty cycle of the regulator's switching based on the
output voltage and current from the regulator. The power factor
controller may be an analog or digital circuit that is operable to
control and minimize or reduce the amount of reactive power
required.
[0054] There are a variety of ways in which the power factor
controller can operate. In one example, the power factor controller
110 receives a pair of signals, via the feedback loop, representing
load voltage and load current, respectively. The load current
signal may be obtained, for example, by measuring the voltage drop
across a known resistance in the power line supplying the load. In
some implementations, the signal lines that deliver these signals
are isolated from the power line via optical isolators (not shown
in FIG. 1).
[0055] In some implementations, the power factor controller 110
integrates these signals to derive respective average values
representing load voltage and load current over time. The power
factor controller 110 then uses the average values to control
switching in the regulator 108.
[0056] In some implementations, the power factor controller 110
also controls the regulator 108 switching to limit the load current
to a predetermined maximum value to thereby protect the load. There
are a number of ways in which this may be accomplished. In one
example, however, current flowing either into the regulator 108 or
out of the regulator 108 is sensed. The power factor controller 110
receives a signal, in some implementations over an isolated signal
line, representing the sensed current. The power factor controller
110 controls the regulator's 108 switching to limit the sensed
current to a predetermined maximum value.
[0057] The output capacitor 114 is provided only to filter very
high frequencies (e.g., those specified to be filtered by the
Federal Communications Commission (FCC) or other regulating or
standards bodies and/or to avoid excessive noise). It does not
filter low frequencies (e.g., frequencies at or around twice the AC
power source frequency and below). The output capacitor 114
generally is a film-type capacitor or a ceramic capacitor. The
exact range of frequencies that the capacitor 114 is designed to
filter can vary from circuit to circuit depending on various design
considerations. In various implementations, it can be sized to
filter out frequencies ranging between about 150 kHz to 3 Ghz. In a
typical implementation, the circuit 100 does not substantially
filter frequencies below the range of frequencies that capacitor
114 is designed to filter.
[0058] In the illustrated implementation, diode 112a and (optional)
diode 112b are connected to the regulator's output and help ensure
that current flows in one direction only (i.e., toward the load
104) under substantially all operating conditions.
[0059] In various implementations, the circuit 100 can include a
variety of other circuit components, including other capacitors,
not shown in FIG. 1. If any of such other circuit elements are
present, however, none would be designed to substantially filter
frequencies at, near or below twice the AC power source
frequency.
[0060] FIGS. 2A-2C show exemplary voltage waveforms that would be
expected to appear at various points in the circuit of FIG. 1 when
an AC power source 102 and a substantially resistive load are
connected to the circuit 100. In these figures, the abscissa
(x-axis) represents time ("t") and the ordinate (y-axis) represents
voltage ("V"). The time scales are the same in each figure.
[0061] As indicated above, during operation, the AC power source
supplies AC voltage (V.sub.IN) to input terminals at the rectifier
106. An example of the AC voltage (V.sub.IN) waveform is shown in
FIG. 2A. This waveform is substantially sinusoidal and is
approximately what might be supplied, for example, from an electric
utility company. In some implementations, particularly in the
United States, this AC input ("line") voltage would be about 120
volts and would have a frequency of about 60 Hz.
[0062] The rectifier 106 produces a rectified AC voltage having a
constant polarity, an example of which is shown in FIG. 2B. The
waveform in FIG. 2B is similar to the waveform of FIG. 2A, except
that, in FIG. 2B the polarity of the previously negative portions
of the waveform has been reversed. All portions of the illustrated
waveform, therefore, are positive. The waveform produced by the
rectifier has a repeating pattern with a frequency that is twice
the frequency of the AC line voltage. If, for example, the AC line
frequency were about 60 Hz., then the rectifier's output frequency
would be about 120 Hz.
[0063] The regulator 100, diodes 112a, 112b, feedback loop with
power factor controller 110 and output capacitor 114 operate to
produce a regulated output voltage that has the same frequency as
and is substantially in phase with the voltage produced by the
rectifier. An example of this output voltage (V.sub.L), which is
sent to the load 104, is shown in FIG. 2C.
[0064] Since the voltage waveform of FIG. 2C is substantially in
phase with an absolute value of the line voltage, the load 104
draws current substantially at the same frequency as the absolute
value of the line voltage. It has been observed that for loads such
as light emitting diodes, the regulated, rectified waveform
typically does not cause the light emitting diodes to visibly
flicker. Nor does the regulated, rectified waveform damage the
light emitting diodes.
[0065] FIGS. 3A-3C show measured operating parameters for a test
circuit that was similar to circuit of FIG. 1 except that the test
circuit did not include diode 112b. The test circuit in this
example was connected to a resistive load of about 75 watts.
[0066] More particularly, FIG. 3A is a screenshot of an
oscilloscope showing measured output voltage 302, FIG. 3B is a
screenshot of an oscilloscope showing measured output current 304
and FIG. 3C is a screenshot of an oscilloscope showing measured
output voltage 302 and measured output current 304 plotted against
the same time axis.
[0067] The output voltage 302 and output current 304 measurements
were produced from a circuit that was receiving an input voltage of
about 120 volt, 60 Hz. As shown in FIG. 3C, both the measured
output voltage 302 and the measured output current 304 have
frequencies of about 120 Hz, that is, approximately twice the
frequency of the AC line voltage. As shown, the measured output
voltage 302 was substantially in phase with the measured output
current 304. Both the measured output voltage 302 and the measured
output current 304 were approximately in phase with an absolute
value of the AC line voltage.
[0068] The measured power factor was 0.939. The total harmonic
distortion (Vthd %) was 1.94, with harmonics components as follows:
3.sup.rd=0.48%, 5.sup.th=1.65%, 7.sup.th=0.9%, 9.sup.th=0.33%,
11.sup.th=0.42% and 13.sup.th=0.45%. The measured line current was
674 milliamps.
[0069] FIGS. 4A-4D show measured operating parameters for a test
circuit that was similar to circuit of FIG. 1 except that the test
circuit did not include diode 112b. The test circuit was connected
to a light emitting diode fixture of about 75 watts as its
load.
[0070] More particularly, FIG. 4A is a screenshot of an
oscilloscope showing measured output voltage 402, FIG. 4B is a
screenshot of an oscilloscope showing measured output current 404,
FIG. 4C is a screenshot of an oscilloscope showing measured output
voltage 402 and measured output current 404 plotted against the
same time axis and FIG. 4D shows a high switching frequency
component 406 of the output current.
[0071] The output voltage 402 and output current 404 were produced
from a 120 volt, 60 Hz. AC line voltage. In the illustrated
screenshot, both the measured output voltage 402 and the measured
output current 404 had frequencies of about 120 Hz, that is,
approximately twice the frequency of the AC line voltage. As shown,
the measured output voltage 402 was substantially in phase with the
measured output voltage 404. Both the measured output voltage 402
and the measured output current 404 were approximately in phase
with an absolute value of the AC line voltage.
[0072] The measured power factor was 0.943. The total harmonic
distortion (Vthd %) was 2.1, with harmonics components as follows:
3.sup.rd=0.39%, 5.sup.th=1.68%, 7.sup.th=1.0%, 9.sup.th=0.29%,
11.sup.th=0.46% and 13.sup.th=0.45%. The measured line current was
552 milliamps.
[0073] FIG. 4D shows a screenshot of an oscilloscope showing a
"switching" high frequency component of output current 406 flowing
into the light emitting diode load of approximately 75 watts. The
illustrated screenshot shows that the switching frequency was about
60 kHz.
[0074] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention.
[0075] For example, the techniques disclosed herein may be applied
to single stage isolated or non-isolated topologies. Additionally,
these techniques may be applied to a variety of converter
topologies including, for example, single ended primary inductor
converters (SEPIC), Cuk converters, flyback converters, forward
converter, and half or full bridge converters. The techniques can
be applied to circuits utilizing any kind of modulation technique,
such as pulse width modulation or frequency modulation.
[0076] The techniques and circuitry disclosed herein can be used to
produce regulated voltage, regulated current, or regulated voltage
and regulated current.
[0077] The techniques and circuitry can be used to supply regulated
voltage and/or current to a variety of loads, including light
emitting diode loads and motor control loads.
[0078] Additionally, one or more high frequency switches can be
used in modulating the pulse width and/or the switching frequency
in the regulator. In some implementations, the modulation is
implemented to limit the peak and/or average load current. Limiting
peak current, for example, helps protect the regulator circuit
and/or the load itself from input surges. Modulation may be used to
regulate output voltage and/or output current.
[0079] Other implementations are within the scope of the
claims.
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